Birth Weight and Thyroxine-Binding Globulin in Pre-Eclampsia

Abstract

Plasma concentrations of thyroxine (T₄) and thyroxine-binding globulin (TBG) as well as triiodothyronine uptake (T₃U) were measured in 32 proteinuric pre-eclamptic patients and 24 normotensive pregnant women at similar gestations in the third trimester. The pre-eclamptic patients had slightly lower TBG, and significantly lower T₄, concentrations, which were significantly correlated. They also had significantly lower infant birth weight which was correlated to the TBG and T₃U values. There was no correlation between T₄ and TBG or between birth weight and TBG or T₃U in the normotensive women. It is likely that the correlation between TBG and birth weight in the pre-eclamptic patients reflects the severity of proteinuria in pre-eclampsia.

Relation between Birth Weight and Thyroid Function in Preeclampsia-Eclampsia

“…As TBG concentration is reported to be lower in unsuccessful pregnancies [17], this decrease may be a useful indicator of placental function deteriora tion in pregnancy [5], We think that the placental dys function may cause failure in estrogen production, there fore decrease in TBG, TT3 and TT4 and simultaneously growth failure to the fetus. We found a significant correla tion between birth weight and maternal TBG levels which was similar to that of Lao et al [5].…”

“…as well as high TSH concentration tended to have low-birth weight babies. Lao et al [5] suggested that the reduced serum concen trations of thyroid hormones in toxemia may in part be explained by the loss of protein and hence protein-bound hormones in the urine. The infant birth weight was found to be related to the maternal serum albumin level in situa tions where there was heavy proteinuria such as the nephrotic syndrome [10], In normal pregnancy, the increasing production of pla cental estrogen during pregnancy stimulates the hepatic synthesis of TBG [11][12][13][14][15], and this is reflected by a decrease in T3U [16].…”

“…The infant birth weight was found to be related to the maternal serum albumin level in situa tions where there was heavy proteinuria such as the nephrotic syndrome [10], In normal pregnancy, the increasing production of pla cental estrogen during pregnancy stimulates the hepatic synthesis of TBG [11][12][13][14][15], and this is reflected by a decrease in T3U [16]. As TBG concentration is reported to be lower in unsuccessful pregnancies [17], this decrease may be a useful indicator of placental function deteriora tion in pregnancy [5], We think that the placental dys function may cause failure in estrogen production, there fore decrease in TBG, TT3 and TT4 and simultaneously growth failure to the fetus. We found a significant correla tion between birth weight and maternal TBG levels which was similar to that of Lao et al [5].…”

“…Reduced TBG levels probably account for the lower TT4 concentration in toxemic patients [5]. Since TT3 is mostly the peripheral conversion of TT4 [18,19], the decrease in TT3 levels associated with low TT4 values is a normal consequence.…”

“…Since pregnancy is generally associated with hyperthyroxinemia, the degree of hypothyroxinemia might reflect the severity of toxemia [2], The pregnant patients who gave birth to abnormal infants showed an important decrease in the level of thyroxine-binding globulin (TBG) at 15-16 weeks gestation [3] and also the relation between a low TBG level and habitual abortion was reported [4], We encountered only a few studies on the relationship be tween thyroid hormones and birth weights in toxemia. One of these studies showed a significant correlation between lower birth weight and TBG as well as triiodothy ronine uptake (TiU) [5]. Another study suggested that birth weight was only correlated with thyroid-stimulating hormone (TSH) [6].…”